: 1996 Deville over heats when ac is on



brojake316
06-21-13, 12:46 AM
Hi I have a 1997 cadillac deville and the temp begins to rise ONLY when the ac is turned on and it will only do that after driving for at least say 20 minutes or so. I really don't think the heads are blown because it only rises and overheats when the ac is turned on and there's no coolant coming out of the exhaust. Im trying to eliminate some possibilities and highlight some others and any help would be appreciated....

Submariner409
06-21-13, 08:55 AM
Go just above this post and read the cooling system/gauge stickys.

Read the Cadillac Technical Archive way up ^^^ in the top black bar.

Check your fan fuses and relays. Do the fans run in SLOW when A/C is requested ?

Here's your pre-2000 cooling fan circuit .................. save it for reference.

Ranger
06-21-13, 12:21 PM
IF your cooling fans are working, it IS possible that you are in the early stages of a HG failure. If so, your overheating will become more frequent.

It may be too early for a block test at this time, but if the fans are not the problem, it might not hurt to give it a shot (after an overheat episode).

brojake316
06-30-13, 03:32 PM
OK I found out that antifreeze is in the groundwater after driving with the ac on. That's obviously where the coolants going. Do y'all know what this can be?

Submariner409
06-30-13, 05:54 PM
Huh ???

If you mean that coolant is mixed with the condensate from the A/C (drips out under the passenger's feet area) then you probably have a failing heater core......... OR one of the heater supply/return pipes across the right (rear, firewall) side of the engine is rusting out.

Ranger
06-30-13, 09:43 PM
Antifreeze in the ground water? :hmm: Are you draining you coolant onto the ground and letting it soak in so that it works it way into your well water?

brojake316
07-01-13, 01:00 AM
Yea submariner that's what I meant the condensate from the ac. Do u know how much that could run to fix?
No ranger I know that wouldn't be good but thanks.

Submariner409
07-01-13, 09:02 AM
If coolant is dripping out of the A/C drain then the heater core is the first suspect. It's a pretty detailed job as a good part of the dash and HVAC system has to be taken out.

If you DIY I would recommend having a real GM service manual on hand, or a subscription to www.alldatadiy.com.

Ranger
07-01-13, 12:13 PM
If the heater core where leaking, wouldn't you see coolant in the cabin on the passengers side carpet before the condensate drain? :hmm:

brojake316
07-01-13, 12:47 PM
OK there's no sign of anything wet on the passenger floor so does that mean its not the heater core? How much would it cost if I had a shop do it? Could you give me an estimate?

Ranger
07-01-13, 10:10 PM
OK there's no sign of anything wet on the passenger floor so does that mean its not the heater core? How much would it cost if I had a shop do it? Could you give me an estimate?
That would be my guess.

Call around and get an estimate from the shop that will do the work. I wouldn't venture a guess.